The known methods involve carrying out a topometric preparation after a diagnosis is determined and a decision is made to use a radiation therapy of a malignant neoplasm by means of X-rays. During the said topometric preparation linear sizes, the square, the volume of pathologic forms, organs and anatomic structures are determined and their relative location in a particular patient are described in quantitative terms (see, for example: Radiation therapy of a malignant neoplasm. Physicians guide. Ed. by prof E. S. Kiseleva. Moscow, “Meditsina”, 1996 [1], pp. 46-47). The main task of a topometric preparation is to combine various data obtained in the course of disease diagnostics, and to provide the radiologist with all anatomical data about the volume to be irradiated, at 1:1 scale in the form, enabling development of an exposure program. For selection between the exposure program options and parameters, it is necessary to know the shape and dimensions of the target site, its location in the patient, as well as syntopy of surrounding tissues, the distance between the target and most important, from the point of view of dosage distribution, anatomical structures and critical organs. In particular, topometric preparation and exposure program development result in identification of the characteristic points and areas on the patient's surface, with respect to which the X-rays are would be subsequently aimed during exposure.
The main disadvantage of the described combination of the patient's preparation for exposure and exposure delivery is that these stages are separated both in time and space, in particular, because they are carried out by different means. Exposure (radiation action on the cells of a malignant neoplasm for the purposes of their killing) is done with the help of rather powerful directional x-ray sources. Concerning X-ray examinations, preceding the exposure, it is done using significantly lower radiation intensities, moreover, each of them is usually only one of several methods, applied in combination: angiography, excretion urography, examination of gastrointestinal tract, bones of a skeleton and skull, and thorax; radionuclidal examinations of bones and liver; ultrasonic methods (echoscopy, echotomography) to obtain images of the organs of the abdominal cavity, pelvis, of soft tissues; computed tomography—a highly effective X-ray imaging technique; magnetic resonance tomography, etc. Therefore it is very difficult to achieve high accuracy of exposure, hence, some parts of the malignant site happen to be unexposed, or intensive X-rays concentrates in the volume, exceeding the dimensions of the said malignant site. If the latter is the case, the surrounding healthy tissues receive a much higher dosage than the healthy tissues inevitably encountered along the path of radiation to the malignant site.
Implementation of such method is affected not only by the errors in selecting reference points and aiming X-rays to the said points during exposure, but also by instability of internal organs and inaccurate positioning of the patient during different exposure sessions. At the same time, radiation fractionation in itself done in an attempt to avoid overdosage on healthy tissues, makes a vicious circle, as it is known, that a doze, delivered once to the malignant site and being sufficient for its irreversible damage, is in several times lower than the cumulative dose required in case of fractionation [1, pp. 84, 91].
Some known technical solutions provide for special measures aimed at better accuracy and patient's position stability, so as to overcome this disadvantage (see, for example, U.S. Pat. No. 5,983,424, published Nov. 16, 1999 [2]).
Another way of overcoming the said disadvantages consists in application of a so-called simulator—an X-ray diagnostic apparatus, the geometric and kinematics capabilities of which are quite similar to teleirradiation apparatus [1, p. 55]. It is possible “to ray” the patient from different directions without changing his position by means of the said simulator. During topometric preparation the patient is placed on the simulator's table in the position, which he will retain during exposure; then roentgenoscopy is done. Using a light cross and movable x-ray contrast fibers, the center and borders of the volume to be exposed is selected and the plane where the central axis of the radiation beam will be during exposure, is marked.
However none of such measures allow avoiding the errors in “aiming” the beams irradiating a malignant neoplasm, because these errors result from tumor growth. This factor becomes particularly significant in case of prolonged treatment, when the exposure sessions are distanced in time from the time of the patient diagnostic examination finalization.
Technical solutions, closest to the suggested inventions, are described in U.S. Pat. No. 5,207,223 (published May 4, 1993 [3]). According to this patent, images of the patient's tissues structure are formed by means of the directed X-ray beams just before exposure, which images are used for the correction of the exposure program versus the results of the preceding diagnostic examinations. However, in this instance different beams are used to form the said images and to produce radiation action on the tissues of the malignant site, which in principle does not cater for errors in orientation of the irradiating beams. Besides, the acceptable accuracy of obtaining the image can be achieved only through realization of the computed tomography algorithms, thus, implying not only complex technical means but a rather high dosage as well.